CSS Error in Formats.less of Enterprise Theme

Could the error be referring to the screen.less file.
Could you provide an export of this file please? 

The Enterprise theme didn't use LESS styling, by default. So, it's likely this may be an error from either an upgraded older version of the Social theme or an edit of the Social theme, running in a newer version of Community that has an upgraded, more precise LESS parser.

Theme files can be edited from the front-end in Manage Site Theme > Edit this Theme. Formats.less is likely in "Supplementary Files". According to the error, it looks to be missing a semicolon at the end of line 261.

So it is possible that 8 didn't use LESS files. I "borrowed" the theme from our external 8.0 site for our internal 8.5 site 3 years ago when we upgraded to 8.5. But I know for a fact that we are using the factory default site theme in 10.1 with minor edits to the variables.less and the Custom Styles. Formats.less is NOT in the social theme. I know for a fact that it is in the Enterprise theme. can verify this by looking at the files in filestorage/themefiles/s/themeID/files. formats.less is in the Enterprise theme and not in the social theme. Regardless of how it got there. 

The issue is with correcting this file in the Enterprise theme. Going to Edit Site Theme only provides access to the currently assigned Site theme, which is Social. The only way to edit any other Site theme is to switch the entire site to that theme, and switching the entire site to Enterprise, even if only temporarily, is not acceptable. 

As I mentioned I have fixed the file that is in the filestorage by directly editing it to get rid of the bad syntax. That does not resolve the issue. So I have to assume that there must be a copy of the theme files somewhere in the database that is only updated when the Admin UI is used to update the them files. The Admin UI that I can't use because I am not on that theme. 

So I am back to the question of how do I edit a Site theme file that is not the current site theme without switching the entire site to that theme? 

The Enterprise theme never used LESS. Version 8 did support LESS, though with a parser that was more lenient to errors. If the Enterprise theme has LESS files, it's been modified. Are you sure formats.less is part of your Enteprirse theme? This would have represented significant modification.

Let me regroup a bit. Enterprise theme implementation goes back to before my time, back when our site was hosted by Telligent at RackSpace. So I can't say how it came to be what it was. And as I think about it I don't think I ever really looked at it. 

When we upgraded to 8.5, our external facing site had recently upgraded to 8.0 using Social theme. They had resources we didn't have, so we borrowed as much of what they did with Social as we could so we could have similar styling without the work. 

So as I look at what we had in 8.5, both Enterprise and Social had the formats.less file. Both have screen.less files. They are different, but exist. Enterprise also appears to have screen.css and other css. So You are right. It was some special thing on our side that put the LESS files in Enterprise.

When we upgraded to 10.1 we made a conscious decision not to do that again. So we intentionally made sure that we completely reverted the social theme to the OOTB version and then we made very few changes to that OOTB version. We didn't want to be that far off the OOTB again. So Our new 10.1 Social is completely disconnected from the Social we used in 8.5. 

Now back to where I stand today. If I look our new Social theme, either in the Admin Edit Theme or just looking at the files in filestorage/themefiles/s/themeID/, the formats.less file does not exist. And if I look at the contents of the screen.less file, it is importing lots of other .less files, but none of them are formats.less. So I can find no evidence that this screen.less/formats.less error notification is related to the Social theme. 

However when I examine the Enterprise theme files those old files are there including a screen.less file that is importing the formats.less file. And the path to that formats.less file is valid and that is the file where I have fixed line 261 to add the missing semicolon. So In theory the file is fixed. 

And I still get the notification. I am going to change the last 2 or 3 groups that are "archived" and not used, but are on Enterprise to Social. And I see if that stops the notifications. 

Thanks for your assistance.